Interfacial perpendicular magnetic anisotropy in Co2FeSi alloy films sandwiched by Pt and MgAl2O4

Abstract

Co2FeSi (CFS) alloy film is one of promising ferromagnetic electrodes and MgAl2O4 (MAO) spinel is an attractive oxide barrier. In this work, we fabricate a series of Pt/CFS/MAO/Pt stacks using sputtering method. For the as-deposited stacks the easy axis lies in the in sample plane. After annealing at 350 °C perpendicular magnetic anisotropy is shown to build in the stacks with CFS thickness ranged from 3.5 to 5.5 nm. A high saturation magnetization of 908 emu/cm3, close to the bulk CFS, is achieved. The perpendicular magnetic anisotropy constant of 105 erg/cm3 in the order of magnitude is witnessed. A large interfacial perpendicular magnetic anisotropy of 1.32 ± 0.18 erg/cm2 is obtained in the annealed stacks. Positive contributions to the PMA from the Pt/CFS and CFS/MAO/Pt interfaces are experimentally confirmed. Significantly improved crystallinity of Pt layers and (1 1 1)-oriented CoPt alloy were revealed by X-ray diffractometry measurements on the annealed stacks, which may be additionally responsible for the PMA.